Log buckers or treelength log cutting apparatus known in the prior art have generally used some type of knuckleboom loader to gather, place, and hold logs or trees in suitable supports for cut off by radial or chain saws mounted on the apparatus.
Hydraulic pressure under manual control has conventionally been used to force such a saw into sawing engagement with the logs, and the saw has frequently stalled because the resistance of the logs to sawing may vary suddenly for reasons of the species, rotten spots or knots in logs, shifting of the logs as they are sawed, and transition of the saw through a stack of logs whereby one log may be engaged at first, then two or more, and finally none as the sawing is completed. Constant and skillful attention by the operator is required to continually feather a control valve to prevent stalling the saw and to keep the saw cutting efficiently at near full sawing capacity.
The present invention provides automatic compensation for the saw engaging hydraulic pressure according to the varying log resistance to sawing, so that the saw can automatically cut with maximum suitable power and without stalling while requiring a minimum of attention and skill from the operator; i.e., the operator merely operates an electrical switch or fully operates a control valve to saw, no feathering required.
In the past, saws of the type to which the present invention is applicable have been conventionally desirably powered from the hydraulic power unit of the knuckleboom loader or some other hydraulic power unit; and especially when the loader is of the "full-swing", or unlimited rotation type where the operator is located on the swinging, rotating portion of the loader, it is convenient to run only two hydraulic hoses from the operator's position through the hydraulic swivel joint connections of the loader to the saw for powering and controlling both sawing and saw engagement.
The present invention provides for powering the saw and engaging it with the logs when one of the hoses is connected to the pressurized fluid and the other to the return line of the power unit, and for automatically cutting off power from the saw and disengaging it from the logs when the hose connections to the power unit are reversed, as by manual operation of a valve at the operator's position. Two hose power and control of the saw is also advantageous for "limited swing" loaders where a switch at the operator's position can control a solenoid valve for reversing the hose connections as aforesaid. In neutral position of the valve, the two hoses to the saw are blocked off, and the pressurized fluid passes freely on to perform other loader functions as selected by operation of other valves connected to the first-mentioned valve.
The sawing force exerted by the teeth of a saw of this general type is conventionally applied in a direction toward the actuating mechanism and point of attachment of the saw to the apparatus, similarly to hand held chainsaw practice, where safety requires it. When the logs shift during cutting with such an arrangement, as frequently occurs, the tendency is for the logs to shift toward the attachment point and often somewhat sideways of the cutting edge of the saw, thereby pinching, wedging, or binding the saw toward its attachment point. Such sideways jamming toward the attachment point tends to be self-wedging, may stall the saw, and can exert great sideways force on the saw with severe damage resulting at the attachment point, in the linkages of a circular saw, or particularly by bending the guide bar of a chain saw close to its attachment point. Not only are parts likely to be bent out of shape, but the saw may become wedged and jammed into the logs so that production must be stopped while the jam is cleared, and it may even be necessary to use hand axes to relieve the jam. Also, cutting toward the mechanism and attachment point means that the resulting sawdust (frequently including sand and dirt) is thrown on and into the working parts with bad effects such as premature wear, corrosion, and labor required for cleanup.
The present invention arranges the apparatus to direct the sawing force away from the mechanism and attachment point so that any log shifting occurs in an outward direction away therefrom, and there is no self-wedging tendency. Thereby, the possibility of saw damage is lessened, as is the skill level required of the operator. Sawdust, sand, and dirt from the sawing will be thrown away from the saw mechanism with resultant benefits as to cleanliness, corrosion, and wear.
While generally symmetrical lugs have been used on the inner surfaces of the log supports to discourage log shifting, the present invention provides lugs of saw-tooth profile with the points oriented to oppose the sawing force which tends to shift the logs.
The distinct advantages provided by the present invention are finding a ready market in the logging trade.